The bug
The player is unable to use some items that can be right-clicked.
How to Reproduce
Get a shield
Spawn a mob
Point the crosshair at the mob and right-click
The shield will not activate.
Affected Items
Shields
Splash potions
Milk buckets
Honey bottles
Buckets (In Creative; milking cows/mooshrooms)
Bowls (In Creative; milking red/brown mooshrooms)
Bows
Crossbows (Loaded/Unloaded)
Tridents
Empty maps
Snowballs
Eggs
I've already reported this in a general ticket (MC-160901), and will add your info from this ticket to mine.